I think this may well be my favorite of the four Tiffany Aching books. If I had to say why... perhaps it's because it has a bit of everything - the chalk and the mountains, the witches and the Feegles, everyday life and deep magic. Or perhaps it's because it's all about boundaries - between all those things and also the edges where the self stops being the self. And it does all that while staying light enough for young children to enjoy. In fact I think it's a nicer read for kids than the first book, which gets a bit metaphysical at times.